GEOL 106 Lecture Notes - Lecture 10: Seismic Wave, Seismometer, Seismogram
5 Jan 2017
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Document Summary
Push pull (p) waves travel faster than standard (s) waves. Through a given material the speed of p-waves is always greater than the speed of s-waves. To measure distance to an earthquake focus we use travel times the time between the p and s wave arrivals at your seismometer. Thunder and lightning example: counting seconds between them: travel time distance graph. To measure distance to an earthquake focus we use travel times: empirically determined travel time curves. Minimum number of seismic stations to locate focus of an earthquake: answer - 3. What energy do earthquakes release: use seismometers. Intensity measurement: mercalli scale, based on observed damage: disadvantages. Each magnitude integer step corresponds to approximately a 30-fold difference in energy release: how much more energy is released in a magnitude 7 earthquake than in a magnitude 5 earthquake 30 x 30 = 900. The largest earthquake ever recorded are ~ 9 on the richter scale.
